Manufacture of fish liver oils



Patented July 9, 1935 UNITED STATES MANUFACTURE OF FISH LIVER OILS Alphonso Thomas Archibald Douglas Middlemass, Penryn, Cornwall, England No Drawing.

Serial No. 706,252. 10. 1933 6 Claims.

My invention relates to a process for the manufacture of fish liver oils. The primary object of my invention is to so treat livers that the oil is rapidly released, and a further object of the invention is to extract oils sweet in odour and taste by providing a method of extraction which can be employed on fresh livers before any marked putrefaction, occurs.

A still further object is to provide a method of extracting oils from livers which will enable the livers to be kept for a considerable period in a fresh state without any discoloration of the final oil. With present day practices, it is essenial that the oil is completely extracted while the livers are fresh, otherwise said oil'is of a dark color, and unpalatable and is thereforefit only for commercial purposes, but if the method herein described is employed the livers may betreated in a very convenient manner, and left for some considerable period, the resultant oil being sweet in odor and taste.

I have found that by treating the livers with glacial acetic. acid, which is substantially free from water, the oil is set free, and if the livers are finely divided such as by mincing, crushing or pulping, and a sufficient quantity of acid added to render the mass slightly acid and lower the pH to approximately 4.6 then said mass may be left for a considerable period usually up to or about fourteen days, the fresh oil being of palatable nature.

If necessary, however, suitable accelerators may be employed to cause the oil to be released almost immediately, and I have alsofound that the combined treatment of livers with an anhydrous neutral salt, such as sodium sulphate and glacial acetic acid results in the almost immediate release of a very large percentage of the liver oil.

The employment of glacial acetic acid lowers the surface tension and therefore aids the release of oil, and further, deposition of stearin is prevented.

In certain cases, for example, in the case of small livers, it is unnecessary to mince or pulp same, as the mere stirring of the mass is sufiicient to effect slight breaking up of the livers.

In most cases, however, the livers are preferably pulped or crushed or minced to ensure intimate contact between the deep-seated tissue and acid.

It is desirable that pulping be effected as soon as possible. Such pulping may be so carried out as to permit of the removal of the hepatic and other veins.

Alternatively, the whole livers after treatment with acid may be heated with agitation if nec- Application January 11, 1934,

In Great Britain January essary of such a nature as to aiit in breaking down the tissue preferably whilst avoiding emulsification.

When livers are not pulped, immediate heating is desirable.

In both cases the whole mass is heated, preferably in a suitable jacketed vessel .to the coagulation point of the protein or beyond that point (to '70 degrees C. or more) for sufiicient time to permit of separation of the oil.

In the case of fresh livers, two distinct layers are formed, one consisting of sludge and the other of oil. After removal of the clear oil the residual sludge may be diluted with water when the remaining oil will rise to the surface.

For example, one hundred pounds (100 lbs.) of the livers of Squalus acanthias are pulped, minced or chopped and approximately 100 ccs. (one hundred cubic centimetres) of glacial acetic acid are added. The whole is well stirred and heated to approximatey degrees C., stirring occasionally.

After standing for half an hour or such longer time as may be necessary to permit of separation, the oil is removed. The remaining portion is then diluted with water, in the case given as an example the sludge is diluted to i0 gallons.

Alternatively the acidified livers may be extracted with suitable solvents either with heat or in the cold. or the oil may be removed from the acidified pulp by other known means.

In certain instances the livers need not be heated, and in this case it may be necessary to allow the mass to stand for a much longer period, up to or about '14 days or more with certain livers, depending on the temperature and the nature of the livers to ensure adequate extraction of the oil, since marked putrefaction will not set in. The oil may be washed and/or heated after separation to remove traces of acetic acid or other known means may be employed.

Suflicient glacial acetic acid must be added to lower the pH to 4.6 approximately, or less and the mass is preferably acid to litmus. It is necessary however, it livers are allowed to macerate in the acid state, that deep seated tissue also has its pH altered.

In other example lbs. of the livers of Molva molva are minced and 100 cos. of glacial acetic acid are well stirred into the mass, which is then acid to litmus.

This mass is heated, preferably in a jacketed vessel and the oil removed. The yield of oil is approximately 40%. The residual liver debris may then be dealt with as below.

1. Extracted with water at suitable temperature by simple dilution, which gives (A) a top layer of oil, (B) a middle layer of liver debris, (C) a bottom layer of water soluble extractives from the liver tissue, the oil being removed and items (B) and (C) dealt with in known manner, or

2. Suitably flavoured and used as human food, or

3. Centrifuged or dealt with by other known means to extract the residual oil and then either used for food purposes or extracted with water to obtain the water soluble factors which can then be dealt with in known manner.

An anhydrous neutral salt, such as sodium sulphate, may be employed in addition to glacial acetic acid, and it has been found that such combined treatment results in the ready denaturing of the protein and the quick release of the oil.

In a practical example of the combined treatment with glacial acetic acid and anhydrous sodium sulphate 100 lbs. of pulped livers of Squalus acanthias are mixed with 15 lbs. of powdered anhydrous sodium sulphate and to the mass is added 100 ccs. of glacial acetic acid. The free oil is removed by known means and the residue may be diluted with water, when more oil is released and floats free of the residual tissue. The addition of a protein coagulant which is also capable of absorbing water reduces the amount of bacterial action and is advantageous in dealing with livers containing a relatively low percentage of oil. Such pulped livers may be treated with sufiicient anhydrous sodium sulphate to coagulate the protein and to absorb the water in the tissue thus leaving the coagulus with a much higher percentage of oil than was present in the original tissue. The coagulated protein may be treated with glacial acetic acid and after mixing be diluted with water and the oil removed by known means or after addition of the acid the mixture can be heated and the oil skimmed oil and after dilution with water the oil can be removed by known means.

Preferably and where convenient the gall bladders are removed from the livers and it will be understood that where an edible substance is produced from the residues after removal of oil the gall bladders must be removed.

I claim:-

1. A process of extracting fish liver oil which consists in adding a relatively small amount of glacial acetic acid to a mass of livers to make the mass acid to litmus and set free the oil, stirring the mass and then allowing same to stand, removing the supernatant oil and treating same to remove traces of acetic acid.

2. A process of extracting oil from fish livers which consists in finely dividing the livers and adding in amount not exceeding one percent of the amount of the livers glacial acetic acid to bring the pH down to 4.6 approximately, and render the mass acid to litmus.

3. A process of extracting oil from fish livers, which consists in finely dividing the livers and intimately mixing therewith glacial acetic acid in amount not exceeding one percent of the amount of the livers to set free the oil.

4. A process in the manufacture of fish liver oil, which consists in finely dividing the fish livers, adding to the mass glacial acetic acid in amount not exceeding one percent of the amount of the livers, and heating the mass to accelerate the denaturing of the protein, and the freeing of the oil.

5. A process for treating raw fresh fish livers to initially and rapidly set free the oil and retard putrefaction which consists in placing the raw livers in a container, adding glacial acetic acid in an amount equal approximately to one percent by volume of the raw livers, and then stirring the entire mass.

6. A process for treating raw fresh fish livers to initially and rapidly free the oil and retard putrefaction, which consists in placing the raw livers in a container, adding glacial acetic acid in an amount equal approximately to one per cent by volume of the raw livers, stirring the entire mass, and subsequently heating the mass of raw livers and acetic acid to approximately C.

ALPHONSO THOMAS ARCHIBALD DOUGLAS MIDDLEMASS. 

